php-java-bridge-users

[Php-java-bridge-users] Caching of (Java) objects (Lucene)

[<php...@li...>]

Hi

I'm looking at the possibilities to keep certain Java objects (in my
case Lucene index searchers, query filters) persistent between client
calls.

I looked at the java_session() function, but this is not possible as I
it interferes with the session functions of the application in which
I'm using the php-java bridge. I also suspect serializing (sometimes
larger) objects is beyond the scope of session variable too.

So my question is if any of you could shed some light or point me in a
good direction to look for the best solutions. I am currently
exploring the idea of using a Java cache framework like Apache Jakarta
JCS but maybe I'm looking to far ...

Any input is very much appreciated

Best regards

Paul

-- 
http://walhalla.wordpress.com

Re: [Php-java-bridge-users] Caching of (Java) objects (Lucene)

[<php...@li...>]

Hi Paul,

> to keep certain Java objects (in my
> case Lucene index searchers, query filters)
> persistent between client calls.

I usually use a factory class:

public class FooFactory {
  private static final Object foo=createFoo();
  public Object getFoo() {
     return foo;
  }
}

This works because the JVM keeps the class Name=>Class
bindings in a weak hash map and classes usually aren't
gc'ed unless the VM runs short of memory.

The above method can't be used if all nodes of a
(weblogoc- or tomcat-) cluster should refer to the
same foo instance or if there's no persistent VM at
all(for example if lucene and the bridge classes have
been compiled to native code and are started for each
request).


> I also suspect
> serializing (sometimes
> larger) objects is beyond the scope of session
> variable too.

Depends on how long you want to keep the data and how
expensive it is to create. If the data is really
expensive I would use the JPersistenceAdapter,
serialize the data and store it on the master node, on
the web server or in a database and deserialize it
when the next request comes in.

Regards,
Jost Boekemeier



		
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Re: [Php-java-bridge-users] Caching of (Java) objects (Lucene)

[<php...@li...>]

Hi Jost

Thank you very much for your explanations

On 7/24/06, php...@li...
<php...@li...> wrote:
> Hi Paul,
>
> > to keep certain Java objects (in my
> > case Lucene index searchers, query filters)
> > persistent between client calls.
>
> I usually use a factory class:
>
> public class FooFactory {
>   private static final Object foo=createFoo();
>   public Object getFoo() {
>      return foo;
>   }
> }
>
> This works because the JVM keeps the class Name=>Class
> bindings in a weak hash map and classes usually aren't
> gc'ed unless the VM runs short of memory.

That could be part of the solution, like a lucene indexreader for a
dedicated application. But in my case, I want to build an easy to
distribute/deploy PHP component requiring only the minimim work of
installing your php-java bridge as a stand-alone service (or for those
who can within tomcat or the likes).

> The above method can't be used if all nodes of a
> (weblogoc- or tomcat-) cluster should refer to the
> same foo instance or if there's no persistent VM at
> all(for example if lucene and the bridge classes have
> been compiled to native code and are started for each
> request).
>

That is not the case for me, I did not explore the option of compiling
to native code yet (but will do, curious about the performance with
respect to a VM install)

> > I also suspect
> > serializing (sometimes
> > larger) objects is beyond the scope of session
> > variable too.
>
> Depends on how long you want to keep the data and how
> expensive it is to create. If the data is really
> expensive I would use the JPersistenceAdapter,
> serialize the data and store it on the master node, on
> the web server or in a database and deserialize it
> when the next request comes in.

Ah, that's interesting! The data (lucene filters and sort objects
mainly) is rather expensive to create (roughly 50 to 200 msec per
instance for a "typical" index which has a few tens to a few hundred
fields and 100k records)

The main problem with JPersistenceAdapter is that I should find a way
to get this working in a PHP4 contextto which I'm tied now ... and
which does not look trivial now

Thank you very much again, I learned a lot andn admire your work on
the php-java bridge!

Best regards

Paul

-- 
http://walhalla.wordpress.com

Re: [Php-java-bridge-users] Caching of (Java) objects (Lucene)

[<php...@li...>]

Hi,


> dedicated application. But in my case, I want to
> build an easy to
> distribute/deploy PHP component requiring only the
> minimim work of
> installing 

the memory cache is the easiest solution I can think
of. 

A file cache requires much more work, every node has
to serialize the data to java.io.tmpdir (that's the
only directory to which J2EE or SEL has write access)
and make sure that all other nodes don't update or
read the cache while one node updates the data.

If the data doesn't fit into memory or into
java.io.tmpdir, you'll need a decicated cache daemon
which listens on some port, updates its database
regularily and answers requests from the nodes. Users
could start this daemon, if they want to: java -jar
luceneCacheDaemon.jar

If a Socket(daemonPort) fails during startup of a node
you could revert to memory cache:

public class fooFactory {
  private static Foo foo;
  private static final Socket cacheDaemon;
  static {
    try { cacheDaemon = new Socket(DAEMON_PORT); }
    catch (IOException e) {/*ignore*/}
  }
  public static synchronized foo getFoo() {
    if(foo!=null) return foo;
    if(cacheDaemon!=null) 
      return foo=getFoo(cacheDaemon);
    return foo = createFoo();
  }
}


> to native code yet (but will do, curious about the
> performance with
> respect to a VM install)

Starting a native lucene .so costs about 100 to 150
ms.


Regards,
Jost Boekemeier



		
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Re: [Php-java-bridge-users] Caching of (Java) objects (Lucene)

[<php...@li...>]

Hi Jost

After some tests I went for a java cache implementation with ehcache.
In this way I did not have to write Java, but more importantly it is
easier to to cache dynamically generated java objects (like query
filters which are different for each user) -- even persistent if I use
the disk cache when the JVM stops.

Now I need to upgrade the bridge to 3.1.7 and install it in a J2EE
server (still running the bridge with a stand-alone JVM)

Best regards

Paul

-- 
http://walhalla.wordpress.com

Re: [Php-java-bridge-users] Caching of (Java) objects (Lucene)

[<php...@li...>]

Hi Paul,

> implementation with ehcache.

thanks for the pointer. Especially its multicast
features sound interesting.


> Now I need to upgrade the bridge to 3.1.7 and
> install it in a J2EE
> server (still running the bridge with a stand-alone
> JVM)

I hope this isn't a big problem. But it was difficult
to maintain two separate implementations, the
standalone component and the J2EE component. 


Regards,
Jost Boekemeier



		
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